Tafsir of Al-Mujadilah 58:16

"They took their corrupt oaths, with which they swear when the need arises, as a junnah," meaning a protection and a screen against accountability. Al-Hasan read it as īmānahum (with a kasra on the hamza), meaning the faith they manifested to the Prophet—may Allah exalt him and grant him peace—and to the sincere believers. It is stated in al-Irshad: "Taking" in this reading is an expression for concealing oneself through action, as if it were said: They used the faith they manifested as a cover so that their blood and wealth would not be made lawful.

According to the reading of the majority, it is an expression for their preparation of their false oaths and their readying of them for a time of need, so that they may swear by them and escape accountability—not their actual usage in the moment, for that comes after the accountability which follows the commission of a crime, and is also after the cause of it. This is expressed by the fa (the 'so') in His saying, the Exalted: "So they hindered [others]"—meaning people—"from the way of Allah" during the time they felt secure, by discouraging those they encountered from entering Islam and by belittling the status of the Muslims in their eyes. It is also said: They hindered the Muslims from killing them, for that is the way of Allah regarding them. It is said that saddū (they hindered) is an intransitive verb, and the meaning is "so they turned away from Islam in reality," though this is as you see it to be.

"And for them is a humiliating punishment."

This is a second threat with a different description of their torment. It is said: The first is the punishment of the grave, and this is the punishment of the Hereafter. The description of it as "humiliating"—which necessitates manifestation—suggests this.